OFFSET
2,1
COMMENTS
a(n) has been computed by Donovan Johnson up to 200, but no values were found below 2*10^11 for n=41, 67, 113, 149, 157, 181.
LINKS
F. Firoozbakht, Puzzle 466. phi(n-1)=phi(n)=phi(n+1), in C. Rivera's Primepuzzles.
S. W. Graham, J. J. Holt and C. Pomerance, On the solutions to phi(n) = phi(n+k) Number Theory in Progress, K. Gyory, H. Iwaniec, and J. Urbanowicz, eds., vol. 2, de Gruyter, Berlin and New York, 1999, pp. 867-882.
Donovan Johnson and Michel Marcus, a(n) for n=2 to 200, with missing terms shown as 0.
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Sep 26 2012
STATUS
approved